1. Field of the Invention
The present invention relates to a fastener driving tool for fastening a fastener such as a nail, rivet, or staple to a member to be fastened.
2. Description of the Related Art
In the related art, spring-driven type fastener driving tools employing electric motors are well-known. This type of spring-driven type fastener driving tool uses the drive power of an electric motor to push up a plunger urged by a spring in a direction from a lower dead point in a fastening direction to an upper dead point in resistance to urging force of the spring. A fastener such as a nail is then driven into a member to be fastened by an accelerated plunger as a result of the plunger being released.
Typically, nail driving equipment is equipped with a mode switching switch for selecting one operating mode of a single driving mode or a continuous driving mode. For example, when the mode switching switch is in single driving mode, the operator presses a push lever (push switch) provided at a nose section that emits nails against a member to be fastened. In this state, the operator fires one nail by pulling a trigger of the trigger switch. It is then not possible for the next mail to be driven in until the operator temporarily releases operation of both the push switch and the trigger switch. When the operator selects continuous driving in mode, the operator can drive in a nail every time the push-switch is pressed against the member to be fastened while the trigger of the trigger switch is pulled in by the operator.
However, recently, it has been necessary for the force with which the plunger is urged by the drive spring to be increased in spring-driven-type fastener driving tools, i.e. the spring energy has been increased in order to increase the drive impact force to make it possible to drive in larger nails. However, when the spring energy is made large, the spring driven-type fastener driving tool has to move the plunger from the lower dead point side to the upper dead point side using the drive power of the electric motor in resistance to a substantial urging force of the spring. This means that a large amount of time is required to move the plunger for the drive in operation. This means that when the operator drives in the nails into the member to be fastened in continuous drive in mode while continuing to pull the trigger switch, a substantial time difference (time lag) occurs from the operation of the trigger switch until the end of the operation of driving nails. The feeling when driving in is therefore poor, and a problem where the driving efficiency is reduced occurs.
On the other hand, in order to ensure the reliability of the fastener driving tool, when the nose section is drawn away from the member to be fastened, it is preferable for the driving of the electric motor to be stopped by the push switch so that an inappropriate driving operation is actively prevented. There are also cases where a continuous driving mode is required in order to increase the ease of use of the fastener driving tool. In particular, in continuous driving mode, when the operator withdraws the push lever of the nose section away from the member to be fastened to quickly, a problem occurs where sufficient operation time for the electric motor cannot be ensured and spring compression due to the spring compression drive unit becomes insufficient. Namely, after the end of driving in the nail as a result of releasing the compressed spring, it is necessary to compress the driving spring back to its initial state using the motor. However, it is not possible for operating time of the motor to be sufficiently ensured by the fast release of the push switch.
In order to resolve the above problems, it is an object of the present invention to provide a highly reliable spring drive-type fastener driving tool that responds without differences with respect to the operation of operation switches such as trigger switches and push switches etc. and is capable of improving the feeling when driving.